Rubella virus genomic RNA has conserved sequences both at the 5'- and the 3' end which we refer to here as cis-acting elements. The cis-acting elements are implicated to be involved in viral replication. Specific host cell proteins with the elements, we have begun to purify and characterize the RNA-binding proteins. To data we have purified, to homogeneity, a 56 kDa protein from Vero76 cells which specifically interacts with both the 5' and 3'cis-acting elements. Studies are in progress to analyze the amino acid sequence of this protein. Oligonucleotides will be synthesized, based on the amino acid sequence, and will be used as probes to isolate cDNA clones for this protein. Characterization of cDNA clones will help us to understand the nature of the protein, which could shed some light on the understanding of the RNA-protein interaction necessary for viral replication.